1. Field of the Invention
The present invention relates to a memory device and fabricating method thereof. More particularly, the present invention relates to a non-volatile memory (ROM) and fabricating method thereof.
2. Description of the Related Art
Non-volatile memory is a type of memory that permits multiple data writing, reading and erasing operations. Moreover, the stored data will be retained even after power to the device is removed. With these advantages, non-volatile memory has become one of the most widely adopted memory devices for personal computer and electronic equipment. Furthermore, non-volatile memory also has the advantages of occupying a small volume, having a fast access speed and consuming very little power. In addition, data can be erased in a block-by-block fashion so that the operating speed is further enhanced.
A typical non-volatile memory comprises an array of memory cells. The horizontally laid memory cells are serially connected through a word line and the vertically laid memory cells are serially connected through a bit line. In general, the strip-like source/drain regions buried within the substrate serve the bit lines. However, because the source/drain regions are buried within the substrate, contacts are required to connect the source/drain regions electrically with an external circuit. In the process of forming such contacts, problems resulting from a misalignment between the contacts and the source/drain regions must be avoided. Although the misalignment problem can be ameliorated through an increase in the width of the source/drain regions, this also increases the size of each device as well. Hence, from the point of view of device integration, this is no a solution.